Torque Converter Lockup w/ CCC removed

brrian

Master Mechanic
Jul 7, 2022
256
254
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Pittsburgh, PA
81 Grand Prix - I'm preparing to swap my V6 to a Buick 350. Since I'm losing CCC, I need to deal with torque converter lockup, which was previously controlled by the computer. I want it to be automatic, not controlled by a switch, and I want it wired into the brakes so it unlocks when the brakes are applied.

I have cruise control & want to keep it. Cruise uses the normally closed terminals on my brake switch. I wondered if a switch existed that has another set of normally closed terminals, and sure enough, I found that 4th gen Camaro/Firebirds have one, pictured below. I got one from Autozone to test & it worked, and once I knew that I went to the junkyard & got the terminals & pigtails that plug into it.

80's Chevy trucks use a TCC vacuum switch (ACDelco #212-331) to control lockup (thanks pagrunt ), & I got one.

I also got the transmission terminal & wiring at the junkyard today.

With all the pieces I need, I mocked it up & wired it to a 12V test light, and it works just as expected. The TCC switch activates at about 5 inches of vacuum and the brake switch will shut it off when the brakes are applied. Here's a video of it working.

So with all of the pieces I need, i'll wire this all up & it'll be plug and play when I swap motors. I might add a small dash light so I can see when it's working, and I might even wire a light into my V6/CCC circuit, then connect this new setup alongside it so I can compare this to factory lockup.

I guess the verdict is out until it's in the car but I feel pretty good about it. Thanks also to Bonnewagon for talking through this with me.

switch.jpg

diagram.jpg
 
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Oct 25, 2019
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Not really. There's a lot more related to the computer than TCC lockout.

I'm thinking it would have only needed RPM and TPS to operate the TCC though? Not sure if the computer's strategy would be a better match for that 350 than what you came up with though.
 

pagrunt

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Sep 14, 2014
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I'm thinking it would have only needed RPM and TPS to operate the TCC though? Not sure if the computer's strategy would be a better match for that 350 than what you came up with though.
Non-CCC vehicles used this set up for the TCC transmissions. Uses engine vacuum for the switch to lock & unlock. Was a OK set up as trucks used it until they got computer control.
 
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maxi426

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Sep 20, 2018
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On your wiring diagram, the vacuum check valve actually functions as a delay valve. I've found that a 10 sec delay relay that is triggered by your circuit and controlling the solenoid is much more reliable. Also, there are adjustable vacuum switches that will allow you to control the point that engine load turns your delay relay on and off. It gives you adjustability as far as vehicle weight, engine combination, converter stall speed, and rear gear. Both of these items can be found on ebay.
 
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brrian

Master Mechanic
Jul 7, 2022
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Pittsburgh, PA
On your wiring diagram, the vacuum check valve actually functions as a delay valve. I've found that a 10 sec delay relay that is triggered by your circuit and controlling the solenoid is much more reliable. Also, there are adjustable vacuum switches that will allow you to control the point that engine load turns your delay relay on and off. It gives you adjustability as far as vehicle weight, engine combination, converter stall speed, and rear gear. Both of these items can be found on ebay.
I saw the adjustable vacuum switch. I'll probably see how this setup works out first and if I want to tweak it I'll put in the adjustable switch.
 
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Bonnewagon

Lost in the Labyrinth
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Sep 18, 2009
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This system looks like a winner to me. My concern would be when it actually engaged. 5" of ported vacuum may be too low a point of engagement but on-car testing will reveal that pretty quickly. When I had T-350C with the switch on the dash I found that I never used it around town. But on the highway it was always on. That worked for me.
 
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78Delta88

Royal Smart Person
Supporting Member
May 23, 2022
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This is the actual kit from summit...

Screenshot_20231008-010323.png

It shows TH700R4, I'm not seeing one for TH350. The TH700R4 is basically a 350 plus overdrive.

The OP switch would go into the port on passenger side all the way forward near the inlet/outlet ports for the cooler.

The hex head plug 1/8 NPT just behind where the kick down cable hooks in is where the OP switch goes.

Screenshot_20231008-174845.png
 
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